This present application relates to a packaging sheet, specifically, a packaging sheet with improved cuttability properties.
Packaging sheets are used for many purposes. One of these many purposes includes thermoforming the sheet into articles, such as trays, cups, etc., which may then be used to package food, non-food, medical and industrial products. Typically, these applications require thermoformable sheets which are non-oriented.
One packaging sheet that is currently used for thermoforming into packaging articles comprises a fully coextruded sheet with polyvinylidene chloride (PVdC) sandwiched between high impact polystyrene (HIPS), with ethylene vinyl acetate copolymer (EVA) used to laminate the central PVdC layer to the outer HIPS layers. This PVdC sheet generally has no significant sticking, forming, cutting, filling or sealing issues when used for thermoforming into articles. However, it is well known that PVdC has many environmental health concerns, with chlorine as the source of many of these concerns. Both the manufacture and the disposal of PVdC produce dioxin, a highly carcinogenic chemical; and many localities do not permit a converter or packager to reprocess or landfill-dispose of packaging materials containing PVdC. As a result, non-oriented chlorine-free materials may be preferred.
A packaging sheet that is currently used comprises a fully coextruded sheet with ethylene vinyl alcohol copolymer (EVOH) sandwiched between HIPS, with high density polyethylene (HDPE) between the central EVOH layer and the outer HIPS layers. (See, for example, U.S. Pat. No. 5,972,447, published Feb. 15, 2007, which is incorporated in its entirety in this application by this reference.) Such a sheet may have a layer structure of HIPS/HDPE/EVOH/HDPE/HIPS or HIPS/tie/HDPE/tie/EVOH/tie/HDPE/tie/HIPS (where “/” is used to indicate the layer boundary). Both structures are non-oriented and chlorine-free. However, both structures are known to have significant forming and cutting issues when used for thermoforming into articles.
What is needed is a packaging sheet that has no significant sticking, forming, cutting, filling or sealing issues when used for thermoforming into articles.